Radome antenna



Apr-'il 28, 1970 H. s. JONES, JR ET AL 3,509,571

RADOME ANTENNA Filed June 16. 1967 Us. Cl. 343-771 4 Claims ABSTRACT OFTHE DISCLOSURE An integrated radome antenna structure fully utilizingthe dielectric material from which a radome is fabricated., Theelemental antenna is a slotted array designed from metallic-plated,dielectric-loaded, wave-guide which is an integral part of the radomeDThe wave-guide is formed on the radome by copper plating the inner andouter surfaces of the radome to form the at longitudinal surfaces of thewave-guideo The edges of the wave-guide are formed by interlacing a meshwire partition transverse to the surface of the radome The result is acompletely enclosed di electric filled cavity for use as an antennaradiator, when slots are placed thereina (CROSS REFERENCE TO RELATEDAPPLICATION Sen No., 417,523 filed Dec., 10, 1964, now Patent No.,3,346,865 by Howard Sa Jones, JrD

BACKGROUND OF THE INVENTION' Airborne or vehicle carried radar equipmentis almost always covered by a plastic or dielectric radome which issubstantially transparent to electromagnetic energy but which providesmechanical protection for the equipment and contributes to thestreamlining on the vehicle. Situated within the radome itself is theantenna system for the radar equipment., Although such structures haveserved their purpose satisfactorily in the past, they have become lesssatisfactory with the increased complexity and sophis-5 tication oftodays modern radar equipment, and there has been a pressing need for areduction in both bulk and cost of radar equipment, With. the advent ofsimple and compact phase shifting devices electrical scanning of radarantennas has become practical, and several actuated an= tenna arrayshave been replaced with xed arrays,1 There has thus resulted somedecrease in size, weight and expense in radar equipment. However, theseimprovements while abating the problem have not eliminated it., Thesearch for other and more adequate solutions has continued focusingattention on the radar antenna structure itselt, and various attemptshave been made to mount the antenna flush with the skin of the vehicleto achieve a reduction in the bulk of the equipmenta Until theapplicants discovered that the antenna could be integrated with theradome, these attempts had not been entirely satisfactory, )In prior artdevices very little use has been made of radomes other than formechanical purposes. However, as described in application SerH No417,523 tiled Dec 10, 1964 by applicant iones, an investigation into thedesign of a class of dielectric-loaded, slotted wave-guide antennassuggested the possibility of incorporating antennas of this type intoradome structures. A further study indicated a high degree ofcompatibility between this type of antenna and radome designs commonlyused in guided missiles, For example, most of the dielectric materialsused today in the construction of radomes are the same as the dielectric substrates used in the design of flat dielectric loaded slot arraysMoreover, the thickness of the material used can be thel samen .ln theabovementioned copending application the ari-- 3,509,57l Patented Apr,28, 197@ tenna described is a slotted wave-guide antenna arrayfabricated as an integral part of' a dielectric radome cir cuit Thewave-guide for the array is formed by drilling holes through the radomesurface at close intervals in rectangular pattern to form the perimeterof the wave-guide section.7 The holes as well as the exterior andinterior surfaces of the radome enclosed by them are electroplated withcopper or other suitable metal, The result is a waveguide section, thebroad walls of which are formed by the plated portions of the inner andouter surfaces of the radome, and the edges of which are formed by theelectroplated holes through the radomeL Of course, provisions are madeto leave radiating slots on the broad exterior face of the wave-guide inthe electroplating process This technique has resulted in a highlysatisfactory and very compact radar antenna system, It has been found inuse, however, that this mode of construction. weakens the radome itselfuIt is therefore an object of this invention to provide a radar antennawhich occupies no space Within the radome, is extremely light weight,and is very inexpensive to .manufacturea lt is another object of thisinvention to provide a radar antenna integrated with the radome whilenot impairing the strength of the radome,

It is further object of this invention to provide a radome-antennaconfiguration which will permit simultane ous manufacture of the antennawith the radomeu BRIEF DESCRIPTION OF THE DRAWINGS The specific natureof the invention, as well as other objects, aspects, uses, andadvantages thereof, will clearly appear from the following descriptionand from the accompanying drawing in which:

FIGURE l is a typical embodiment of our invention utilizing acylindrical radome section which is cut away to give a side view of theslotted wave-guide.

FIGURE 2 is another embodiment of our invention shown in a conicalradome which has been cut away to give a top-crosssectional View of theslotted wave-glide section,

FIGURE 2a: is a view of the bottom broad wall and the wires forming theedges ot' the `.waveguide section shown in FIGURE 2., ""i

FIGURE 3 is a side cross-sectional view of the wave guide section of theembodiment of FIGURE l showing the means by which a signal is coupled tothe antenna.

DESCRIPTION OF T PREFERRED EMBODIMENTS Referring to FIGURE l of thedrawings, there are shown slotted wave-guide antenna arrays 11 and 12fabri cated as an integral part of a cylindrical dielectric radomesection 10 A side view of slotted wave-guide antenna array 1]. is shownby cutting away a portion of radome 10 so that an isometriccross-section is obtainede Radome l@ is of a conventional type made ofxyybeeglass, but the entire interior surface 17 of radomeldhasheenplatedwith copper., The edges of wave-guide section 11 are formed by lacingwire 13 through the thickness of the radome transverse to its surfaces.The laced wire pattern, such as that shown in FIGURE 1, formed by wire13 is a coniiguration that will minimize the radiation ofelectromagnetic energy along the edges while at the same timemaintaining the strength of the radome at this juncturea TheA portion ofthe outer surface of radome 10 within the perimeter formed by laced wire13 is plated with cop per to form the broad outer Wall 14 of wave-guidesection ille. As a result of the above described construction technique, a radome-antenna combination of sufficient strength to withstandthe rigors of a military environment sangen is obtained with electricalcharacteristics similar to the radome-antenna combination described in'application Ser., No. 417,523, mentioned above Another embodiment ofour inventionis shown in FIG. URE 2. In this embodiment the laced wiredescribed in the embodiment of FIGURE 1 is replaced with rigid wiresspaced close together in vertical position in a rectangular pattern toform the edges of: the wave-guide. In FIGURE 2 a conventional conicalfiber glass radome is shown with a section thereof cut away to revealthe construction of the slotted wave-guide. Although not shown in thefigure, the entire interior surface of radome 20 is copper plated, aswas the case in the embodiment of FIGURE 1, Rigid wires 23 are placed ina vertical position on the interior copper plate in a rectangularpattern so that a wave-guide, such as that shown in FIG- URE 1, will beformed. The wires 23 must be placed closely together to minimize theelectromagnetic energy that could be radiated along the edges, while atthe same time maintaining the strength of the radome at this juncture.Once the wires are in place, the resin impregnated glass filamentwinding layers are interlaced through the wires until the desired radomethickness is achieved. When the radome is subjected to its curingtemperature under pressure, it will produce a unified solid structure.The top broad Wall of the wave-guide can then be formed by copperplating the outer surface of the radome 20 within the perimeter formedby wires 23.

The mode of construction described in FIGURE 2 is more clearly shown byreference to FIGURE 2a in which is shown a thin metal sheet 25 whichwould form the interior surface of the radome. Wires 23 are placed in avertical position in a rectangular pattern on the metal sheet.tSheet 25with wires 23 in place is positioned on the mandrel that is used tolay-up the radome, and the layers of ber glass are placed on sheet 25being interlaced through wires 23.

In FIGURE 3 is shown the means by which a signal is coupled to theradome antenna described in FIGURE 1 or FIGURE 2. In FIGURE 3 is shown aside cross-secm tional view of the radome-antenna of FIGURE 1 in whichlike numbers describe like elements. The waveguide antenna is excitedfrom a standard coaxial waven guide input 31 located along alongitudinal center line a length equal to one quarter wave length ofthe signal to be transmitted in the dielectric medium away from the rowof wires 13 forming an end wall of the wave guiden The -at dielectrichas a low impedance and matches very well with a 50 ohm coaxial input Anantenna system designed as an integral part of a radome fully utilizingthe dielectric radome structure herein described has been developed andconstructed. The results of an evaluation of the electrical performancewere excellent compared with those of conventional systems and theantennas constructed as herein described d have been found to havesufficient strength to withstand the stresses and strains introduced bymilitary applications.,

It will be apparent that the embodiments shown are only exemplary andthat various modification can be made in construction, such as usingdifferent dielectric materials, different plating metals and platingprocesses, and arrangement, such as different antenna congurations,within the scope of the invention as defined in the appended claims;

We claim:

'1. An integral radome-antenna structure comprising:

(a) a radome made of thin low loss dielectric material having aninterior and exterior surface, the interior surface of said radome beingcompletely plated with a conductive metal,

(b) a metal wire partition perpendicular to the inm terior and exteriorsurfaces of said radome enclosing an area of said surfaces of saidradome and placed between said surfaces,

(c) said exterior surface of said radome being plated with a metalwithin the perimeter formed by said partition, whereby said partitionand the portions of said interior and exterior surfaces of said radomeenclosed by said partition form a wave-guide.

(d) at. least one radiating slot in an exterior surface of saidwave-guide,

(e) connecting means adapted to receive a signal to be transmitted andto conduct said signal into said wave-guide.

2. The integral radome antenna of claim I in which said connecting meansis positioned a distance equal to one-quarter wave length of the signalto be transmitted from an end of said wave-guide on the longitudinalcenter of said 'wave-guideB 3. The integral radome-antenna of claim Iwherein said partition comprises a wire laced through the thickness ofsaid radomeD 4. The integral radome-antenna of claim 1 wherein saidpartition com-prises a plurality of vertical wires set in said platedinner surface of said radome, said wires being perpendicular to saidinner surface and extending to said outer surfaceH References CitedUNITED STATES PATENTS 2,761,137 8/1956 Van Atta et al. 343--7853,155,975 11/1964 Chatelain a 343-785 ELI LIEBERMAN, Primary ExaminerUSt CL XR, 343-708, 872

